Carboxy-terminated composite rocket propellant and process for producing using an amide additive



Nov. 4. 1969 .FIG.I

FIG.2

' FIGS MAXIMUM STRESS SHORE HARDNESS STRAIN AT MAXIMUM STRESS TADAMASA HARADA ET AL 3,47 C ARBOXY-TERMINATED COMPOSITE ROCKET PROPELLANT AND PROCESS FOR PRODUCING USING AN AMIDE ADDITIVE Filed D80. 20, 1967 NO. I

o l I 1 T l l I l I l O 2 4 6 8 IO I2 I4 I6 I8 2O CURING DAYS l l l I I -60 50 4O 30 20 IO O IO 20 3O 4O 5O MEASURI N6 TEMPERATURE IOO MEASURING TEMPERATURE United States Patent US. Cl. 149-19 7 Claims ABSTRACT OF THE DISCLOSURE A composite propellant consisting of a fuel binder mainly comprising liquid organic compounds containing carboxyl group, an epoxy group-containing compound and/or a cyclic imine groupcontaining compound, and anoxidizing agent characterized by having present in the propellant composition an amide compound.

There is also disclosed a process for producing the above-mentioned composite propellant.

BACKGROUND OF THE INVENTION This invention relates to a composite propellant (hereinafter referred to as prope1lant) and a process for producing the same, and, more particularly, it relates to an improvement in the mechanical properties of such propellant by incorporating a novel material thereinto.

Field of the invention There have been known heretofore propellants consisting of a fuel binder mainly comprising liquid organic compounds having carboxyl group in their molecules and epoxy group-containing compounds and/or cyclic imine group-containing compounds, and an organic or inorganic oxidizing agents.

The curing reaction of the fuel binders is described in Rubber Chemistry and Technology, p. 932, vol. 36 (1963) and the preparation of the propellant using these fuel binders is described in the specifications of US. Patent Nos. 3,147,161 and 3,149,009.

In general, the propellants are, after the production thereof followed by transportation and storing, combusted in rocket engines under a pressurized condition to utilize the total impulse generated at that time.

Throughout the series of these steps, the propellants are subjected to various static or dynamic stresses exerted thereon and the propellants must endure the deformation and destruction caused therefrom. Thus, the propellants are required to have a combination of excellent combustion performance and mechanical properties.

Although the mechanical properties of the propellants are variable by changing the type of fuel binder, the type and amount of oxidizing agent used and the type of modifier used to improve the combustion performance, the improvement in the mechanical properties of propellants is now chiefly relying upon the alteration of type of fuel binder used, since the type and amount of oxidizing agent and the type of modifier may not be changed due to the necessity for preserving the combustion performance of the propellants. Moreover, the mechanical "ice properties of propellants tend to be deteriorated because the propellants normally contain 40-90 parts by weight of powdered solid oxidizing agent.

The most conventional compound of liquid organic compounds containing carboxyl group which relate to the propellant of this invention is carboxylated polybutadiene.

The carboxylated polybutadiene mentioned above is a typical example of fuel binder for a propellant at present because it has advantages in that the propellant containing the same shows superior mechanical properties at low temperatures and delivers higher energy over the propellants using the conventional fuel binders such as polysulfide, polyurethane, etc.

However, the propellant containing carboxylated polybutadiene has a drawback in that it has poor mechanical properties at temperatures in the vicinity of room temperature. Thus, there have been exerted considerable efforts for eliminating the drawback accompanied by the propellant containing carboxylated polybutadiene and such efforts have been unsuccessful so far.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a composite propellant having improved mechanical properties.

It is also another object of this invention to provide a process for producing a composite propellant having improved mechanical properties.

More porticularly, the object of this invention is to improve the mechanical properties of a propellant containing a fuel binder which is obtained by adding epoxy group-containing compound and/or cyclic imine groupcontaining compound to liquid organic compounds having carboxyl group in their molecules, and, if required, incorporating a catalyst, a plastizer and a filler into the resulting mixture, and curing the same by the reaction of carboxyl group with epoxy group and/or cyclic imine group. The fuel binder mentioned above may be referred to as ester-type fuel binders.

We have found thatthe object mentioned above can be fully accomplished by incorporating an amide compound into the conventional ester-type fuel binders known heretofore.

The mechanical properties of the propellant may be remarkably improved by the incorporation of an amide compound into the propellant composition at the time of preparing the same, preferably at the time of preparing the ester-type fuel binder.

The oxidizing agents which may be used in the propellant of this invention in the amounts ranging 40-90% by weight based on the total weight of the propellant can be any type of conventional organic or inorganic solid oxidizing agents. For example, perchlorates and nitrates of metals, ammonium or hydrazine; organic nitro compounds and addition products of perchloric acids of organic compounds may be used.

The fuel binders which may be used in the propellant composition of this invention are most preferably those having rubbery properties obtained by a polymerization reaction or a cross-linking reaction of a liquid organic compoundhaving not less than 2 carboxyl groups in its molecule with compound having epoxy group and/or compound having cyclic imine group.

The liquid organic compounds having carboxyl groups which may be used in the propellant composition of this invention include, copolymers or terpolymers obtained by polymerizing at least one of vinyl compounds such as methylmethacrylate, acryonitrile, vinyl chloride, vinylidene chloride, fiuoroethylene and styrene, conjugated diene compounds such as butadiene, isoprene and chloroprene, unsaturated hydrocarbon compounds such as ethylene, propylene and acetylene, with acrylic acids; organic compounds obtained by carboxylation of homopolymers or copolymers of conjugated diene compounds and aromatic vinyl compounds; and a mixture of two or more kinds thereof. Typical examples of the organic compound include carboxyl-terminated polybutadiene, polybutadieneacrylic acid copolymer, and butadiene/acrylic acid/acrylonitrile terpolymer.

Typical examples of organic compounds containing epoxy group which may be used in the propellant composition of this invention include bisphenol A glycidyl ether, 1-epoxy-3,4-epoxy-cyclohexane, polybutadiene polyepoxide, oleic acid glyceride cpoxidate and fatty oil epoxidates, and any organic compounds having at least 2 epoxy groups per a molecule thereof may be conveniently used.

Typical examples of compounds containing cyclic imine group which may be used in the propellant composition of this invention include trismethylaziridinyl-phosphine oxide, trisaziridinyl-phosphine oxide, imine-terminated polymer, phenyldimethylaziridinyl-phosphine oxide, tripropylene melamine, triethylene melamine, and hexamethylene bisethylene urea. Any organic compound having at least 2 cyclic imine groups such as ethylene imine and propylene imine groups per a molecule thereof may be conveniently used.

These epoxy group-containing compounds and cyclic imine group-containing compounds may be used either alone or in admixture with two or more kinds.

The epoxy group-containing compound or cyclic imine group-containing compound is used in an amount of more than 0.5 equivalent, preferably 0.8-5.0 equivalents, calculated for the epoxy or cyclic imine group based on carboxyl group of the liquid organic compound.

The amide compound newly incorporated thereinto has active hydrogen which reacts with these cyclic compounds. At times, the cyclic compound to react with carboxyl group is shorted due to the reaction mentioned above, thus, there is added 3.0 equivalents, preferably 0.21.0 equivalent, of epoxy group and/or cyclic imine group based on the total active hydrogen of the amide compound in order to replenish the shortened amount.

The epoxy group-containing compound and/or cyclic imine group-containing compound which react with the active hydrogen of amide compound, and those which react with carboxyl group of the liquid organic compound can be the same or different.

Amide compounds which may be used in the propellant composition of this invention are those having at least one NHCO group per a molecule thereof and generally having the following chemical structures:

wherein R, R, R and R' represent saturated or unsaturated hydrocarbon having 1-30 carbon atoms which may contain 0, N, S, Si, halogen and/or organo-cyclic compounds; B and B which may be the same or different represent NH; and/or COOH, l and n are values of 0-6, and m is a value of 0-1000, preferably 0400, most preferably 0-30, provided that m is not less than 1 when l and n are both zero, and the above-mentioned R may be H y hen l is zero, ega dless f he va ues of m an I! No particular restriction is imposed on the type of amide compounds so long as they have the chemical structure defined above. In general, the amide compounds may be easily and conveniently obtained by reacting organic amines at 70 to 300 C. in the conventional way with carboxyl group of all types of carboxylated compounds including saturated monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, capric acid, lauric acid, palmitic acid, and stearic acid; olefinic monocarboxylic acids such as acrylic acid, isocrotonic acid, crotonic acid, vinyl acetic acid, methacrylic acid, pentenoic acid and octenoic acid; acetylenic monocarboxylic acids such as propiolic acid, tetrolic acid, undecynoic acid and stearolic acid; diolefinic acids such as 2,4-pentadienoic acid, diallylacetic acid and 9,12-octadecadienoic acid; higher monocarboxylic acids such as linolenic acid and linoleic acid; halogen-substituted saturated or unsaturated monocarboxylic acids such as chloroacetic acid, iodoacetic acid, fiuoroacetic acid, bromoacetic acid, a-ChlOI'OprOplOtliC acid, p-chloropropionic acid, a-bromopropionic acid, B-bromopropionic acid, a-iodopropionic acid, p-iodopropionic acid, a,a-dichloropropionic acid, a,;8-dichloropropionic acid, a-chlorocapronic acid, a-chloroacrylic acid, a-bromoacrylic acid, fi-bromoacrylic acid, ,B-chloroacrylic acid, ot-chlorocrotonic acid, and B-chlorocrotonic acid; saturated or unsaturated dicarboxylic acids and halogen-substitutes thereof such as malonic acid, succinic acid, gultaric acid, adipic acid, pimelic acid, sebacic acid, azelaic acid, maleic acid, fumaric acid, itaconic acid, methylfumaric acid, acetylenic dicarboxylic acid and muconic acid; oxy acids such as malic acid, tartaric acid, citric acid, acetoacetic acid and lactic acid; cyclic carboxylic acids such as benzoic acid, cinnamic acid, salicyclic acid, gallic acid, phthalic acid, terephthalic acid; isophthalic acid, trimesic acid and dicarboxybiphenyl; and carboxylic acids containing halogen, oxygen, nitrogen and sulfur as represented by carboxylate compounds containing furan, pyran, thiophene, pyrol, pyridine and pyrimidine rings.

Since it is interminable to list all of these carboxylic acids and derivatives thereof, these enumerated above are only a part of examples, and acid chlorides, acid anhydrides and esters of these carboxylic acid may also be used.

No particular restriction is imposed on the type of amines to be reacted with carboxylic acid so long as they contain NH group. Although it is interminable to list all of these amines, a part of examples include saturated and unsaturated monoor poly-amines and oxyamines such as methylamine, propylamine, butylamine, hexylamine, octylamine, methylenediamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, triaminopropane, tris (2-aminoethyl) amine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylene imine, vinylamine, allylamine, propargylamine oxyhexylamine, aminopropan diol and aminopropanol; amino acids such as alanine, aminobutyric acid and glycine; cyclic amine or organo-cycle amines such as aniline, phenylenediamine, naphthylamine, diethoxydipropylamine silicate and melamine; amines such as hydrazine and urea; and halogen substituted derivatives thereof.

The amide compounds which may be used in the propellant composition of this invention may also be obtained by a reaction of isocyanates such as tolylene diisocyanate and hexamethylenediisocyanate with compounds having active hydrogen, such as alcohols, acids and amino acids, or halogenated alkylmagnesium. Moreover, they may also be obtained by reacting carbonyl compounds such as acetone and methylethylketone with ammonia.

There are many variety of reactions which afford the amide compounds and any of these reactions may be conveniently used.

The amide compound is incorporated into the propellant composition in an amount of (ml-5.00%, preferably -0.051.0% by weight based on the weight of the propellant, for a satisfactory result. The amounts either less than 0.01% or more than 5% lead to unsatisfactory result.

In order to fully manifest the effect on the improvement in the mechanical properties of the propellant composition by the incorporation of amide compounds thereinto, it is desirable that the amide compounds may be mixed with uncured fuel binder as uniformly as possible. However, there is required no particular art for the mixing process and a simple grating machine commonly used may be conveniently used. In fact, the composition can be mixed by hand, if the amount is small and if the amide compound is crushed sufficiently.

The amide compound is incorporated into the composition when uncured ester-type fuel binder, oxidizing agent and combustion performance modifier are mixed together, preferably when mixing the uncured ester-type fuel binder alone, and mixed well.

After the ester-type fuel binder, oxidizing agent and combustion perforance modifier are sufficiently mixed and bubbles present are removed, the resulting composition is cast into a desired shape and cured by heating at 40-150" C. for 1-300 hours to give the composite propellant of this invention.

As described above, the ester-type fuel binder consists of a major portion comprising liquid organic compound having carboxyl group, epoxy group-containing compound and/or cyclic imine group-containing compound and a minor portion comprising a curing catalyst, a plasticizer and a filler, which may be suitably selected and incorporated, if required.

Although the curing catalyst is normally unnecessary when a compound having cyclic imine group is used, it is often necessary when an epoxy compound is used as a major portion of a cross-linking agent. Any curing catalysts may be conveniently used in the propellant composition of this invention and no particular restriction is imposed on the type thereof.

Examples of these curing catalysts include metal salts of organic acids such as cobalt naphthenate, cobalt octoate and iron naphthenate; amino compounds such as urotropin, 2,4,6-tris-dimethylaminophenol, and ethylenediamine; inorganic salts and/ or oxides such as Fe(NO and ZnO; complex compounds or chelate compounds such as alcohol complex compounds of metal chlorides, methacrylatochromic chloride and ferrosacetylacetonate; and Lewis acids such as AlCl ,CuCl and SnCl These curing catalysts are normally incorporated into the fuel binder in an amount of 010% by weight.

While any plasticizers conventionally known may be conveniently used, the examples include organic acid esters such as dibutyl phthalate, diethyl phthalate and dioctyladipate; plasticizer containing phosphorus such as tricresyl phosphate; various process oils; formalic plasticizers; and liquid diene polymers.

These plasticizers are incorporated into the fuel binder in an amount of 0-5 0% by weight.

Likewise, any conventionally known fillers may be conveniently employed and the examples include carbon blacks known as channel black and furnace black; silicic anhydride and surface treated products thereof; and metal oxides such as ZnO and TiO These fillers may be incorporated into the fuel binder in an amount of 030% by weight.

The combustion performance modifiers which may be used in the propellant composition of this invention include powders of metals or alloys such as Be, B, Al, Si, Mg, Li and Na; organo-boron compounds and boron hydrides, and organic nitro compounds, all of which enumerated heretofore are effective for increasing the specific impulse of the resulting propellant; metal oxides such as PC3203, F6 0 CUCI'O4, K2CIO4, (NH4)2CT207, V205,

6 CuO, C00 and NiO, and metal salts such as LiF and SrCO which are effective for increasing or decreasing the combustion rate of propellant.

These combustion performance modifiers may be incorporated into the propellant composition in an amount of 0-40% by weight based on the weight of the propellant composition.

Although examples of the curing catalysts, plasticizers, fillers and combustion performance modifiers are given above, they have relatively little to do with this invention, regardless of the selection of the types or even the use thereof. Strictly speaking, in a given composition consisting of ester-type fuel binder, oxidizing agent and combustion performance modifier, if amide compound is incorporated thereinto, the mechanical properties of the propellant obtained therefrom is improved as compared with those of propellant obtained from the composition to which no amide compound is added.

The effect of this invention is so remarkable that the objects of this invention can be fully accomplished, and, furthermore, there can be obtained some additional effects as described in the following.

According to this invention, there is brought about a remarkable improvement in both maximum stress and strain at maximum stress of the resulting propellant composition in a tensile test which evaluates the mechanical properties thereof, e.g. increased by 1.5-3 times as compared with those of compositions known heretofore.

Referring to the accompanying drawings:

FIG. 1 illustrates the relationship between shore hardness and curing time.

FIG. 2 illustrates the relationships between the maximum stress and the measuring temperature in the propellant composition of this invention and that of prior art known heretofore. It is shown that the sample No. 9 which is a typical product obtained according to this invention has larger maximum stresses at respective temperatures as compared with the sample N0. 10 which is a conventional product known heretofore.

FIG. 3 shows the relationships between the strain at maximum stress and the measuring temperature in the propellant composition of this invention and that of prior art known heretofore. It is clearly shown in FIG. 3 that the sample No. 9 has larger strain at maximum stress at respective temperatures, thus, the addition of amide compound has remarkably improved the mechanical properties of the resulting propellant composition.

Although the reason for the improvement in the mechanical properties of the propellant composition by incorporation of amide compound thereinto has not been fully, understood, presumably the reasons are that the mechanical properties of the fuel binder have been improved and that the adhesive force between the fuel binder and oxidizing agent has been enhanced.

It is further presumed that these amide compounds react with epoxy groups and/or cyclic imine roups so that amide groups are bound to main chain or side chain of the 'fuel binder in the propellant composition by Way of a chemical bonding, thus, improving the mechanical properties of the resulting propellant composition.

In, accordance with this invention, there are obtained the following additional effects besides the main effect described above.

In the first place, the rate of curing of the composition is increased. Normally, the propellant of this type is obtained by mixing the respective ingredients, removing bubbles present and casting the resultant mixture and curing the shaped composition by heating. Thus, the increasing in the curing rate brings about advantages in that the time required in the curing process can be reduced, that the number of casting dies which are normally expensive can be reduced, and that the curing room can be made smaller. Hence, the manufacturing cost can be lowered because the manufacturing equipment is made simpler and smaller.

In general, when the rate of curing is increased, so-

called pot life, i.e. the period during which the pro-' cut were removed, the resulting mixture was cast into a desired shape and cured by heating at 70 C. for 5 days.

After the mix was cured, the Tensile Test as set forth in JIS-K6301 was performed at C. The results are shown in Table 1.

Also, in order to now the rate of curing of the present propellant composition in the curing process, the relationship between the Shore hardness and the curing days was measured.

An example of the results obtained is shown in FIG. 1. The Shore hardness was measured according to ASTM 1706-59T, Type A.

TABLE 1 Sample N 0 1 2 3 4 5 6 7 8 Composition: 1

CTPB 13. 8 13. 4 13. 4 13. 4 13. 4 13. 4 13. 6 13. 6 E828 2.3 2.7 2. 7 2.6 2.6 2.7 2.5 2. 5 C-1 2 9. 4 O. 4 0.4 0. 4 0. 4 0. 4 0. 4 0. 4 DBP. 3.5 3.5 8.5 3.5 3.5 2.5 2.5 3.5 Amide compound: a

Type- AM-l AM-2 AM-3 AM-4 AM-5 AM-G AM-7 Amount 0. 2 0. 2 0. 2 0. 2 0. 2 9. 2 9. 2 APCl-.. 80. 0 80. 0 80. 0 80. 0 80. 0 80. 0 80. 0 80. 0 Al powder- 19. 0 10.0 10. 0 10.0 10.0 19. 0 19. 0 10. 0 Characteristics:

Maximum stress (kgJcmJ) 5.0 10. 1 9. 5 8. 0 8. 5 9. 0 12. 1 11. 5 Strain at maximum stress (percent) 27 70 65 60 72 55 65 67 l Compositions are indicated in parts by weight.

2 O-1" is curing catalyst and a mixture of an isopropyl alcohol solution of methacrylatochromic chlorlde and pyridine in a ratio of 1:1 was used.

8 Amide compounds having the following structures were used:

AM-i- HOOCCHaOHiCO(NHCHaCHgNHCOCHzOHiCm NHCHiOHzNH,

Arr-2E In the third place, the mechanical properties can be improved.

In the third place, the mechanical properties of the propellant composition at low temperatures can be improved.

The accompanying drawings, FIGS. 2 and 3 show that the propellant composition according to this invention has larger maximum stress and strain at maximum stress at temperatures ranging from 50 C. to 50 C. as compared with the propellant compositions known heretofore.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention may be explained more fully and practically in the following examples. It should not be construed, however, that these examples restrict this invention as they are given merely by way of illustration.

Example 1 This example illustrates the effect of addition of amide compound with respect to a fuel binder obtained by curing a carboxyl-terminated polybutadiene (hereinafter referred to as CTPB) with bisphenol A glycidyl ether (a product of Shell, E828). The above-mentioned CTPB is obtained by carboxylating a liquid polybutadiene.

There were first mixed CTPB, E828, dibutylphthalate (hereinafter referred to as DBP), a curing catalyst and an amide compound, together at room temperature, and to the resulting mixture were added ammonium perchlorate (hereinafter referred to as APCl) and powdered aluminium (hereinafter referred to as Al powder). After the ingredients were mixed well and bubbles pres- HOOCCHsCHzCO (NH(CH2 INHCOCHICH2CO)DNH(OHR)CNH H0oCCHiCHZNHCOCHZCHiCONHCHiCHiCOQH (C:HsO)zSi(OCzH5NHCOCHiCHaCOOH): (C2 s):N(CHz)iNHCOCH=CHCOOH As shown in Table 1, the incorporation of amide compound remarkably improves the mechanical properties, e.g. the maximum stress at 20 C. by 1.6-2.4 times, and the strain at maximum stress by 22.7 times as compared with those of propellant composition to which no amide compound is incorporated.

It can also be noted from the Table 1 that the eifect of incorporation of the amide compound becomes apparent with the amount of about 0.2% and that there is required only a very simple operation in which the amount of the epoxy group-containing compound added is somewhat adjusted depending upon the amount of active hydrogen contained in the amide compound.

FIG. '1 shows that the sample No. 2 to which amide compound is incorporated reaches a leveled hardness much earlier than sample No. 1 to which no amide compound is incorporated. Samples Nos. 3.8 to which amide compound was incorporated reached a leveled hardness as early as sample No. 2.

Example 2 Various propellant compositions were prepared using the same CTPB as used in Example 1 according to the same procedures as described therein by varying the types of compounds having epoxy group or ethylene imine group thus varying the curing catalyst, to conduct the Tensile Test. The composition of the samples and the results of the test performed are shown in Table 2.

In the instant example, an amide compound of the type AM-l as used in Example 1 was employed.

Samples Nos. 9 and 10 were subjected to the Tensile Test at temperature ranging from minus 50 C. to 50 C. and obtained the results as shown in FIGS. 2 and 3.

TABLE 2 Sample Nos 9 10 11 12 13 14 15 16 Composition: 1

CIPB 15. 0 14. 8 15.0 14. 8 16. 6 16. 4 16. 6 16. 4 Cross-linking agent: 2

Type Q-l Q-l Q-l Q-l Q-Z Q-2 Q-3 Q-3 Amount 2. 7 2. 6 2. 7 2. 6 1. 4 1. 3 1. 4 1. 3 Curing catalyst: 5

Type. C-1 0-1 0-2 0-2 0. 3 0. 8 0. 3 0. 3 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 0 0. 3 0 0. 3 0 0. 3 0 0. 3 80. 0 80. 0 80. 0 80. 0 80. 0 80. 0 80. 0 80. 0 A1 powder 10. 0 10.0 10. 0 10.0 10. 0 10.0 10. 0 10. 0 Maximum stress (kg/omfi) 6. 3 17. 1 4. 2 7. '11. 0 19. 1 8. 5 13. 2 Strain at maximum stress (percent) 58 22 59 58 25 1 Composition is indicated in parts by weight.

2 Cross-linking agents are compounds having epoxy or ethylene imine group which may be further identified as follows:

Q-l is a mixture of E828 and epoxide of fatty oil in a ratio of 1:1.

Q-2 is a mixture of tris (methyl'aziridinyD-phosphine oxide and epoxide of fatty oil in a ratio of 2:1, and

Q,3 is a mixture of tripropylene melamine and epoxide of fatty oil in a ratiqof 2:1 3 As for the curing catalyst, 0-1 is the same catalyst as used in Example 1 and 0-2 is acetonate, urotropin and A101 in a ratio of 1:1:1.

a mixture of ferrosacetyl Nora-The other symbols have the same meaning as defined in Example 1.

It can be seen from Table 2 that although the mechanical properties of the propellant composition are dependent upon the curing catalyst and cross-linking agent used, the mechanical properties are remarkably improved when amide compound is incorporated to the composition, i.e. the maximum stress and strain at maximum stress are increased by 1.5-2.7 times as compared with those of composition to which no amide compound is incorporated.

FIGS. 2 and 3 show that the propellant composition to which amide compound is incorporated has larger maximum stress and strain at maximum stress over a wide temperature region as compared with those of compositon to which no amide compound is added.

Sample No. 10 was prepared repeatedly for 5 times according to this invention to see the reproducibility. The relative tolerance in the maximum stress and strain at maximum stress among these samples remained within the range of -5%, showing an excellent result.

Example 3 Samples Nos. 17, 18, 19 and 20 were prepared according to the same procedures as described in Example 2. However, the CTPB used for samples Nos. 13 and 14 were replaced by butadiene-acrylic acid copolymer (h-ereinafter referred to as PBAA) and butadiene-acrylic .acid-acrylonitrile terpolymer (hereinafter referred to as PBAN) obtained by the radical initiated polymerization.

The Tensile Test was performed at 20 C. and obtained the results as shown in Table 3.

The results show that the mechanical properties of the propellant composition are improved by the incorporation of amide compound, even if the type of the compound containing carboxyl group is altered.

1 Composition is indicated in parts by weight. Nora-Other symbols have the same meaning as defined in Examples 1 and 2.

We claim:

1. In a composite propellant consisting essentia ly of (a) a fuel binder comprising at least one liquid organic compound (i) containing a carboxyl group,

said compound (i) being selected from the group consisting of a copolymer or a terpolymer obtained by polymerizing a vinyl compound, conjugated diene compound, unsaturated hydrocarbon compound or mixture thereof with an acrylic acid, a carboxylated homopolymer or copolymer of a conjugated diene compound or an aromatic vinyl compound, and a mixture of said compounds,

(b) a compound (ii) selected from the group consisting of an epoxy compound having at least two epoxy groups per molecule and a cyclic imine compound having at least two imine groups per molecule, and

(c) an oxidizing agent, the improvement characterized by having present in said propellant (d) an amide having at least one NHCO group per molecule and being represented by a formula selected from the group of formulae consisting of wherein R, R" and R are radicals selected from the group consisting of unsubstituted saturated and unsaturated hydrocarbon radicals having from 1 to about 30 carbon atoms and said radicals substituted with oxygen, nitrogen, sulfur, silicon, halogen or an organic'cyclic radical; B and B are the same or different and are NH or COOH; R is hydrogen or a radical defined by R, R" and R; l and n are Zero or whole numbers from 1 to 6, and m is zero or a whole number from 1 to 1000, and when l and n are both zero m is greater than zero and when l is zero R is only hydrogen.

2. The composition of claim 1 wherein at least a member selected from the group consisting of a curing catalyst for said fuel binder, a combustion performance modifier, a plasticizer and a filler, is further incorporated in said propellant.

3. The composition of claim 1 wherein said amide is present in an amount of 0.0l-S% by weight based upon the weight of the propellant.

4. In the manufacture of a composite propellant consisting essentially of from about 10 to about 60 parts by weight of a fuel binder compound (i) of claim 1, a compound (ii) of claim 1, and 40-90 parts of an oxidizing agent, the improvement characterized by incorporating from about 0.01 to about 5% by weight of an amide (d) of claim 1 based on the weight of said propellant into an uncured fuel binder, removing bubbles from the resultant mix, and curing the resulting composition !by heating the same at a. temperature of from about 40 to about C.

for from about 1 to about 300 hours.

5. The composition of claim 1 wherein said epoxy compound (ii) is selected from the group consisting of bisphenol A glyeidyl ether, 1-epoxy-3,4-epoxy-cyclohexane, polybutadiene polyepoxide, oleic acid glyceride epoxidate and fatty oil epoxidatt- 6. The composition of claim .1 wherein said cyclic imine is selected from the group consisting of trismethylaziridinyl-phosphine oxide, trisaziridinyl-phosphine oxide, imineterminated polymer, phenyldimethylaziridinyl-phosphine oxide, tripropylene melamine, triethylene melamine, and 1 hexamethylene bisethylene urea.

7. The composition of claim 1 wherein the fuel binder is an ester-type fuel binder.

References Cited UNITED STATES PATENTS 0 BENJAMIN R. PADGETI, Primary Examiner U.S. Cl. X.R. 

